From six minutes to twenty seconds - regional AIS exchange in the Baltic Sea and the OpenRisk II project

Blog by Hermanni Backer Johnsen, Åbo Akademi University

One key output of our Openrisk II project will be an extension and development of the Norwegian AISyRISK risk assessment system (aisyrisk.no) to the Baltic Sea. The AISyRISK model calculates, in a cost-efficient, transparent and easily repeatable manner the risk for maritime accidents in a given sea area and time range. This enables monitoring of accident risk developments over time, including the effectiveness of implemented safety and response measures. This feature of AISyRISK has the potential to greatly improve the efficiency of joint measures to enhance the safety of navigation and responses to accidental spills in the Baltic Sea region.

As can be guessed from its name, the AISyRISK model uses AIS (Automatic Identification System) data on ship movements as key input which, in principle, is readily available in the Baltic Sea. However, as the AISyRISK requires AIS data with a very high temporal resolution (20-second resolution) we had to begin our journey by convincing the coastal Baltic Sea EU countries, Norway and European Maritime Safety Agency (EMSA) to upgrade the entire regional Baltic Sea intergovernmental AIS data exchange system from its original resolution of 6 minutes (360 seconds). In this article we will have a closer look at this exciting and substantial contribution the OpenRisk II project has made to the regional AIS data infrastructure, benefiting a much wider group of activities than our project itself. But to understand and appreciate this development properly, it makes sense to begin by taking a closer look at AIS and the regional AIS data exchange system in the Baltic Sea.

The Swedish and Baltic Sea origins of AIS technology

An AIS transponder is a maritime safety device which allows all vessels equipped with one to, continuously and automatically transmit key information such as their identity, position, speed and course and to receive the same information from all the other ships within the maximum range of the used VHF radio. Using AIS, ships have an overview of the traffic around them, even outside line of sight or in zero visibility, and thus increase navigational safety for everyone involved. In 2001 the use of AIS devices was designated by the International Maritime Organization (IMO) Assembly as mandatory for commercial ships via an amendment to the Safety of Life at Sea (SOLAS) Convention. Today, practically all commercial ships carry an AIS device. Use is mandatory for all IMO registered vessels – even if military vessels have the right not to use it and some situations warrant switching it off.

Many readers may be aware of the existence of this AIS data via online services such as marinetraffic.com, where it is displayed as arrows filling the world’s seas. But fewer are aware of the Swedish and Baltic Sea origins of this technology. A key person behind the AIS concept as a navigation safety system is the Swedish professional mariner Benny Pettersson, who got the original idea already in 1965 when on board a ship in a zero-visibility hurricane off the coast of Japan (SMA 2018). However, the concept could have remained an idea only without the invention of key technologies such as the ingenious Self-Organized Time Division Multiple Access (STDMA) datalink, invented by Hans Lans – another Swede. From the initial research and development project launched in 1990 by Pettersson at his working place of the time, the Swedish Maritime Administration (SMA), maritime AIS was developed to a mature technology in the Swedish maritime ecosystem including SMA, other parts of the Swedish administration and industrial partners (e.g. SAAB). Work in Sweden driven by the team at SMA , including Pettersson, Bo Tryggö, Håkan Lindley, Rolf Zetterberg and others, as well as their international partners allowed the 2001 approval by IMO. An important early step in internationalization was the 1991-92 joint Swedish-Finnish project on transmitting DGPS corrections to GPS data via AIS (SMA 2018).

From ship safety to shared regional situational awareness

New uses for AIS data were also invented – beyond the original ship-to-ship safety function. They realised that they could give SMA and other national authorities such as Vessel Traffic Services (VTS) and Maritime Rescue Coordination Centres (MRCC) full overview of traffic over large areas by capturing AIS data by a network of coastal antennas and displaying the resulting data stream on Electronic Navigational Charts (ENCs). A pilot AIS antenna network testing this approach, covering the Swedish coastal waters and the large lakes, was established in 1997 (SMA 2018).

In the wake of the March 2001 Baltic Carrier accident, the largest oil spill in Baltic Sea since the Antonio Gramsci accident of 1979, this approach was extended to the whole Baltic Sea. At the September 2001 extraordinary HELCOM Ministerial Meeting on safety of navigation in Copenhagen, the coastal countries of the Baltic Sea agreed to establish by 2005 a regional network of coastal AIS antennas and a system for sharing the resulting Baltic Sea AIS data. This network was established as planned and in 2005 (HELCOM 2006) the Baltic Sea became the first sea in the world where the countries shared a joint situational awareness of commercial ship traffic based on AIS (HELCOM 2009).

In 2005 the coastal countries chose Denmark (Danish Maritime Authority, DMA) as the host organization responsible for collecting AIS data streams of individual countries, joining them and retransmitting the compiled regional AIS data to all participating countries.  By 2010 this regional data stream from DMA was also shared with the EMSA as a basis of its new systems to EU member states. Thus, the Baltic Sea community developed the AIS exchange system which is the foundation of modern maritime safety systems in Europe and worldwide. The hosting task was later, in 2017 transferred to the Norwegian Coastal Administration.

As the Baltic Sea AIS dataset was fairly big for the computer systems available during launch of the network in 2005, it was agreed that DMA would downsample the original data to 6 minutes between each position report from a ship. This temporal resolution of the data remained valid for 18 years until the start of the OpenRisk II project in 2023.

New use cases for AIS data create a need for higher temporal resolution in the Baltic Sea region

In the highly complex archipelago of the Baltic Sea, and in situations where ships meet each other in close quarters, the six minutes resolution of the Baltic Sea AIS data may easily lead to erroneous artifacts where the tracks of ships appear to cross each other or sail over islands or dangerous shallows. In 2023-24, during the early stages of the OpenRisk II project it was realised that significantly more detailed AIS data with a 20-second resolution would be needed to allow for more correct representation of ship traffic, and accident risks, in the AISyRISK system.

Accordingly, the OpenRisk II project submitted a document to the HELCOM AIS EWG meeting 16 April 2024, requesting such high temporal resolution AIS data from the coastal countries directly – as well as proposing to increase the resolution of the shared Baltic Sea AIS system. Based on the document submission and presentation by the OpenRisk II project, the participating countries and EMSA decided to test increasing the resolution. Successful tests were carried out during Autumn 2024, and the regional Baltic Sea AIS network had switched over to the much finer 20 second resolution by March 2025. Thus, with the help of a gentle push from the OpenRisk II project, the Baltic Sea made again AIS history by being the first region in the world where such high-resolution data is available across national borders.

With the high-resolution AIS data exchange in place, the Baltic Sea region is now all ready for the AISyRISK system implementation by the Norwegian Coastal Administration under the OpenRisk II project!

The author Hermanni Backer Johnsen served 2012-2018 as the Maritime Secretary of HELCOM, responsible for coordinating the work of the HELCOM Maritime Working Group and its subgroups including the HELCOM AIS EWG.

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